The class of π-conjugated polymeric compounds (also referred to as conductive polymers or as synthetic metals) has been the subject-matter of numerous publications in the last few decades.
Owing to the considerable delocalization of the π-electrons along the main chain, these polymers exhibit interesting (non-linear) optical properties, and, after oxidation or reduction, are good electrical conductors. These compounds will therefore probably take on a leading and active role in various practical fields of application, for example in data storage, optical signal processing, suppression of electromagnetic interference (EMI) and solar energy conversion, and also in rechargeable batteries, light-emitting diodes, field-effect transistors, circuit boards, sensors and antistatic materials.
Examples of known π-conjugated polymers include polypyrroles, polythiophenes, polyanilines, polyacetylenes, polyphenylenes and poly(p-phenylenevinylenes). A particularly important and industrially utilized polythiophene is poly(ethylene-3,4-dioxythiophene), which exhibits high conductivity in its oxidized form and is described, for example, in EP 339 340 A2. An overview of numerous poly(alkylene-3,4-dioxythiophene) derivatives, in particular poly(ethylene-3,4-dioxythiophene) derivatives, their monomers, syntheses and applications, is given by L. Groenendaal, F. Jonas, D. Freitag, H. Pielartzik & J. R. Reynolds, Adv. Mater. 12, (2000) p. 481-494.
To achieve very high conductivities, there is employed in situ polymerization methodology, in which the monomeric ethylene-3,4-dioxythiophene is reacted with oxidizing agents, for example iron-III tosylate, in solution to give a highly conductive layer of oxidized poly(ethylene-3,4-dioxythiophene). This procedure is utilized, for example, for producing capacitors.
Although there is thus a variety of very suitable techniques for preparing conductive poly(ethylene-3,4-dioxythiophene)s, there is a need for further improvements. In particular, routes and intermediates are sought which facilitate very rapid formation of conductive poly(ethylene-3,4-dioxythiophene)s.
This need is met by providing novel, optionally substituted 3,4-alkylenedioxythiophene dimers and trimers.